This invention relates to a color image forming system, and, particularly to a color image forming system comprising a scanning exposure unit for obtaining a color image by scanning a beam of light on a light-sensitive silver halide photographic material (hereinafter, sometimes referred to a light-sensitive material).
As a scanning type color image forming apparatuses, those using the thermal transfer system and the ink-jet system have been known in the prior art. However, these apparatuses were insufficient in resolution, reproduction of tone (delicate tone) and reproduction of texture, and thus high quality images could not be obtained.
For obtaining high quality image which satisfy the above-mentioned requirements, most preferred is a method in which exposure is carried out by scanning exposure apparatus on a silver halide light-sensitive material.
A principle of obtaining a color image by means of the so-called optical scanning exposure unit in which a beam of light is scanned on a light-sensitive material will be described below.
Color image data separated into the three colors B, G and R are converted to light intensities of correspondingly different wavelength bands, and scanning is made on a light-sensitive color photographic material by use of the light of these. The scanning herein mentioned, which may be made by moving the light or by moving the light-sensitive material, means the relative movement of light to the light-sensitive material. Used as the light-sensitive material are those having spectral sensitivity distribution corresponding to the intensity distribution of the three kinds of light to be used. The light-sensitive material receives the light signals having been modulated into intensities with the three kinds of spectral sensitivities on the basis of the color image data of the respectively corresponding B, G and R, and is color-formed in a suitable manner depending on the light signals, whereupon a color image can be obtained.
Known as three kinds of light sources are those using the three colors B, G and R. Known as the light sources are combination of white light sources such as glow lamps, xenon lamps, mercury lamps and tungsten lamps with filters; light-emitting diodes, gas lasers, solid lasers, semiconductor lasers and so forth. In general, coherent lasers are often used as the light sources in view of the high luminance, focusing performance, monochromatic sensitivity, etc. Specifically, the blue light source includes a He-Cd gas laser (441.6 nm) and an Ar.sup.+ gas laser (488.0 nm); the green light source, an Ar.sup.+ gas laser (514.5 nm), a He-Ne gas laser (543.5 nm); and the red light source, a He-Ne gas laser (632.8 nm). However, in instances where conventional Ar.sup.+ gas lasers are used as a blue light source and a green light source, respectively, the peak wavelength of the light sources thereof are adjacent each other and are not consistent with the peak of the spectral sensitivity of the conventional light-sensitive material, and therefore, color turbidity in a blue-sensitive layer and a green-sensitive layer are caused, resulting in inferior image quality. For this reason, if the green-sensitive source is replaced with a He-Ne gas laser and the blue light source employs the Ar.sup.+ gas laser as it is, the color turbidity in the blue-sensitive layer of the light-sensitive material cannot be solved, although the color turbidity in the green-sensitive layer can be solved. On the other hand, in instances where the blue light source is replaced with a He-Cd gas laser and the green light source employs Ar.sup.+ gas laser as it is, the color turbidity in the green-sensitive layer cannot be solved, although the color turbidity in the blue-sensitive layer can be solved.
Further, the above Ar.sup.+ gas laser have problems such as unstable, expensive, short in life and large in scale of the unit.